1. Technical Field of the Invention
The present invention relates to tires with a radial casing reinforcement, and particularly to the protection of the crown reinforcement of such tires.
2. The Related Art
Tires intended to be driven under difficult conditions, for example on surfaces with stones or sharp objects, usually have a crown reinforcement comprising a working block and a radially external protective block. The working block is designed to take up the forces resulting from inflating and rolling of the tire. The protective block is designed to protect the plies of the working block against damage caused by impacts and perforations suffered during use, and comprises at least one ply of parallel reinforcing threads. These reinforcing threads often have an elongation at break which is higher than that of the working plies they protect.
To improve the fatigue strength of the crown reinforcement of such a tire, patent application WO 99/00260 (U.S. Pat. No. 6,460,587) discloses a tire comprising a crown, two sidewalls and two beads, a casing reinforcement anchored in the two beads and a crown reinforcement, the crown reinforcement comprising radially, from the inside outwards, a working block and a protective block with at least one ply of substantially circumferentially oriented parallel reinforcing threads, in which the protective ply consists of elastic metallic reinforcing threads. In this tire, the working block ply adjacent to the protective ply consists of inextensible metallic reinforcing threads.